Defibrillators restore a patient's heart to normal operation by discharging a storage capacitor through paddle electrodes held against the chest. Inasmuch as they are only used is life-or-death situations where time is of the essence, it is imperative that their operation be made as simple as possible. It is often necessary to change the amount of charge on the capacitor before discharging it. In present equipment, this is done by bringing the paddle electrodes together so as to discharge the capacitor, setting the charge control to a desired charge level, and initiating the charging action by depressing a charge button. When the desired energy level is reached, charging is terminated.